Electrical condenser



Y G.l P. SMITH ELECTRICAL CONDENSER l Filed March 5, 1944 Divin. hei v fNNa Aug. 6, 1946.

Patented Aug. 6, i946 ELECTRICAL CONDENSER Gail P. Smith, Corning, N. Y., assignor to Corning Glass Works, Corning, N. Y., a corporation of New York Application March 3, 1944, Serial No. 524,896

2 Claims.

The present invention relates to fixed electrical condensers and more particularly to a condenser wherein the capacitance must be held within close tolerances.

The prime object of the present invention is a xed condenser whose capacitance can be readily reduced to a predetermined Value.

Another object is a novel method of so making a Xed condenser that its capacitance can be readily reduced to a predetermined value after assembly,

Other objects and features of the invention will present themselves in the course of the description of the invention.

The preferred embodiment will now be described as applied to the form of condenser disclosed in a Bair application for Condenser and method of assembly," Ser. No. 524,908, filed concurrently herewith and assigned to the assignee of the present application.

in the accompanying drawing Fig. l diagrammatically illustrates a heating and pressing apparatus by means of which cer tain steps of the invention may be carried out, and also shows an assembled strip of condensers embodying the invention being conveyed into the furnace;

Fig. 2 is a diagrammatic View illustrating a suitable arrangement for driving conveying and pressing rollers associated with the furnace of Fig. l;

Fig. 3 is an exploded perspective view of an assembly embodying the invention as prepared for passage through the furnace;

Fig. 4 is an elevation of a strip of condensers embodying the invention; and

Fig. 5 is a perspective View illustrating the step of separating a strip of condensers into individual condenser units` Referring now to Fig. 3, the assembly as prepared for passage through the conveyer furnace of 1, comprises a strip of sheet metal II of dimensions appreciably greater than a strip of condenser assemblies to be assembled thereon. Arranged on strip I I is a chalked asbestos pad I2 upon which is superimposed a strip of glass nlm I3. Individual condenser elements or sheets I 4 of metal foil are then arranged in laterally spaced relation on strip I3 with one edge of each sheet I4 set inward from the edge of a strip I3 and with the opposite edge of each sheet projected well beyond the opposite edge of the strip, the latter edge of the strip serving as one tab or terminal of a condenser assembly. A second strip of glass nlm I5 is then superimposed en sheets I4 and vertically aligned with strip i3. The next layer of the assembly is composed of laterally spaced metal foil sheets I6. Each sheet I6 is like sheets Ill but projects over the opposite edge of strips I3 and l5 and serves as the other tab or terminal of a condenser. A third strip of glass film I'I is then arranged over sheets I4 in vertical register with strips I3 and I5. The number of alternate layers of foil sheets and strips of glass lm employed is of course determined by the capacitance of the condensers desired. For the purpose of simplicity a condenser strip having but three layers of metal foil has been shown.

To enable one to readily reduce the capacitance of the completed condenser to a predetermined standard value, the metallic sheets of the final layer are flagged and each branch of a sheet made available for separation from the sheet, thus enabling the capacitance of a condenser to be reduced in one, two or more increments. To provide the foregoing feature, narrow strips I3 of mica are arranged on the glass strip Il a small distance inward from the edge over which the final layer of metal foil sheets are to project, and serve to prevent a narrow cross-sectional area of the attached ends of the flagged sections of the final layer of foil sheets i9 from later becoming bonded to the glass strip VI. After placement of sheets le on strip I1 a narrow strip 2i! of glass iilm is arranged to cover those portions of sheets I9 projecting to the left (Fig. 5) of strips I8.

The glass strip may be severed transversely between the individual condenser units in any conventional glass severing manner. Applicant prefers, however, to employ the thermal shock severing method taught and claimed in his application, Ser. No. 524,897, filed concurrently herewith. As taught by said application, Nichrome or similar wires 2l are nextarranged on glass strip 25 transverse thereto Wherever it is desired to later sever the assembled strip. As illustrated, the wires 2I are arranged outside the edges of the endcondenser pile-ups to trim excess end portions of the glass strips therefrom and are also arranged intermediate adjoining pile-ups to separate them from one another. Wires 2l and the underlying assembly is next covered with a chalked asbestos pad 22, which is then covered with a pad 23 of coarsely woven material of glass or asbestos cloth or the like, and the whole covered by a sheet metal plate 24 and the assembly placed on those rollers 25 at the left end of the furnace assembly.

Rollers 25 and pressing rollers 26 and 21 are all driven by a single motor 28 as required to adaeoasae vance material through the furnace at a uniform predetermined speed. i

Specifically the motor 28 is coupled to a gear reduction unit 35 which, by means of a chain 36, drives pressing roller supporting shaft 3l in a clockwise direction while the rollers 25 receive their drive from shaft 3l through chains 38 and 39. Pressing roller 26 is on the other hand driven in a counter-clockwise direction by interposition of a pair of gears lill in a drive between shaft 3l and shaft GI carrying pressing roller 26.

The pressing of the assembly is for producing an intimate void-free bond between the metal and dielectric layers. The pressure necessary to accomplish this, of course, depends on the number of layers in the particular assembly being manufactured. The pressure applicable by rollers 25 and 2l has accordingly been made adjustable by the use of scale beam weighted levers 50 exerting downward pressure on the upper pressing roller shafts 4 l.

The furnace proper comprises a pre-heating section 3d, a heating and pressing section 3l and an annealing section 32. As diagrammatically illustrated, each of the sections 30, 3l, `and 32 contains a pair of electric heating elements. rThe electric current supplied to the elements of the respective sections of the furnace is so adjusted that the temperature maintained Within section 3@ is such that an assembled strip of condensers attains a uniform temperature near lthe softening temperature of its glass strips by the time it starts entering section 3l and reaches or slightly exceeds the softening temperature just before entering pressing rollers 26 and 2l. The temperature of section 32 is so adjusted that the strip issues therefrom with the glass in a strain-free condition and at a temperature approaching room temperature.

The strip, after issuing from the furnace, is divided into individual condensers or into laterally spaced groups by including the Nichrome wires 2l in `an electric heating circuit, as illustrated in Fig. 5, whereupon the wires are heated and severance effected by thermal shock, As separation is effected, the Nichrome wire also breaks away from the glass and may be again used.

As will be appreciated, accuracy of placing the foil sheets in exact predetermined positions in the condenser pile-ups is essential if capacitance are to be held within a predetermined narrow capacitance range. With this fact in View, plate lI may have score lines ll to indicate to the assembler the distance inward from the glass strips at which the foil sheets are to be place-d. As a further precaution against shifting of the foil sheets and glass foil strips, the respective strips and sheets may be temporarily glued to one another. With metal plate l I arranged on a suitably heated hot plate, diphenyl may be used as the temporary adhesive, as it will be volatilzed as the assembly passes through section 35i of the furnace. If desired, the mica strips i8 and wires strips i3 do not bond to the mica.

2l may also be temporarily glued to the assembly to assure their remaining in place until they are bonded to the assembly. The `asbestos pads l2 and 22 and the cloth 23 provide a cushioning action which compensates for slight irregularities in the glass films and prevents excessive fracture of glass strips of the assembly while being subjected to the pressure of rollers 26 and 2l. The chalking of asbestos pads I2 and 22 prevents objectional sticking of the glass to the pads.

While the pressing of the assembly is taking place, the wires and metal foil are Wet by the softened glass and becomes thoroughly bonded thereto. Obviously, the glass strips of the assembly at the same (time become bonded to one another wherever they overlap the foil sheets and in the areas between pile-ups. It will be appreciated therefore that the strip issuing from the furnace comprises a unitary body of glass having imbedded therein and thoroughly bonded thereto the metal parts of the assembly.

As will be appreciated, the transverse flagged sections of sheets I 9 arranged over the mica The condenser capacity, accordingly, can readily be reduced by removing one or more of the unbonded portions from a sheet I9. As will be appreciated, if a greater range of adjustability is desired, the flagged sheet i9 can be duplicated in the bottom of the assembly.

What is claimed in the instant application:

l. A condenser assembly comprisingl a pile up of sheets of fusible dielectric material in the form of lm with metallic elements in the form of foil arranged between and having portions overlapped by the respective sheets, said sheets being in intimate contact with said elements and being fused to one another in those portions which overlap said elements, at least one of said elements being branched and exposed near the unbranched end by the overlying sheet with means holding transverse sections of the exposed portions of the branches separated from the underlying sheet of dielectric material whereby such sections are free for removal from the adjoining fused on portions of the branches.

2. As a new article of manufacture a condenser pile-up comprising alternate layers of metal foil and glass lrn bonded to one another, the alternate layers of metal projecting beyond different margins of the glass for electrical terminal connections and one of the two outside layers of metal being divided into a comb-like member with the unattached ends of the teeth covered by glass to a point near their ends of attachment, and a strip of mica separating a transverse section of the exposed teeth from the underlying `glass thereby preventing bonding of the metal thereto so that fracture of any tooth can be readily effected to reduce the capacitance of the condenser.

GAIL P. SMITH. 

